UTILIZATION OF FISH OIL BY CANDIDA LIPOLYTICA AND GEOTRICHUM CANDIDUM

Abstract

Attempts were made to maximize biomass production in the oxidation of fish oil by Candida lipolytica Y1094 and Geotrichum candidum Y552 in shake flasks. Maximum biomass was produced on 5% w/v oil in water containing 1.5% (NH4)2 SO4, 2.2% KH2PO4, 0.12% MgSO4, 0.03% fish stickwater solids, 10 ppm FeSO4 · 7H2O, 1.5 ppm MnSO4 · H2O, and adjusted to pH 7.5. For G. candidum 40 ppb biotin were added to the medium. When inoculum size was varied from 1 to 8% v/v, the most appropriate inoculum size was about 2%. Aeration rates were increased by decreasing the medium volume per 500-ml shake flask. Maximum yields were obtained with 25 ml of medium. Cell recoveries were complicated by formation of oil-media emulsions. Several methods of biomass recovery were studied. Warming the acidified cell suspension in the presence of Triton X-100 allowed removal of oil from the cell mass. Extraction of the dried cell mass with ethyl ether yielded highest recovery of cell material compared to other methods. Dry cells contained 40.1 to 49.3% crude protein. These studies suggest the feasibility of obtaining 800 g of single cell biomass with a crude protein yield of 320 g from 1 kg of fish oil using batch or continuous culture systems.